The present invention relates generally to bearings and more particularly to rolling element bearings such as ball bearings.
In an aluminum plant (as well as other plants such as steel plants and ceramic and brick manufacturing plants), metal is transported for treatment into a furnace or heat treatment oven by a furnace car which, like a train, is typically mounted on flanged rollers for driving along rails. A furnace car may typically remain in a furnace for as much as 24 hours or longer under ultra high temperatures which are typically in the range of 700 to 1100 degrees F. As used in this application and the claims, the term xe2x80x9cultra high temperaturexe2x80x9d is meant to refer to a temperature in the range of about 700 to 1100 degrees F., and the term xe2x80x9cultra high temperature bearingxe2x80x9d is meant to refer to a bearing which is used in an application wherein the bearing is normally subjected to an ultra high temperature.
Sinter cars are used to transport sinter (raw material for steel) which is heat treated as the sinter car transports the sinter some 300 feet. A sinter car wheel has two rolling surfaces, i.e., one used as a guide for the car, similar to a train wheel, and the other which is engaged by a sprocket which empties the car. Sinter car wheels as well as pellet car wheels experience high temperatures in the range of about 250 to 650 degrees F. The furnace car wheels for bottom car furnaces, wherein the top of the car becomes the bottom of the furnace when the car is pulled into position, also experience such high temperatures since the wheels are insulated from the ultra high furnace temperatures. As used in this application and the claims, the term xe2x80x9chigh temperaturexe2x80x9d is meant to refer to a temperature in the range of about 250 to 650 degrees F., and the term xe2x80x9chigh temperature bearingxe2x80x9d is meant to refer to a bearing which is used in an application wherein the bearing is normally subjected to a high temperature. Sinter and pellet car wheel bearings are also subjected to high contamination from dust and the like as well as high temperature. The seals are often inadequate against the onslaught of contaminants with the result that the grease in the bearings is quickly rendered ineffective.
In both furnace and sinter and pellet car wheel bearings, the high or ultra high temperature melts the grease, causing it to come out of the bearing, or bakes the grease out. As a result of these harsh environmental conditions, conventional furnace and sinter and pellet car wheel bearings must regularly (perhaps each time used) be re-greased through a grease fitting and must often, due to contamination of the grease, be taken apart, cleaned up, and repacked with fresh grease, consuming much down-time and labor, at great expense.
It is accordingly considered desirable to provide a bearing which is low maintenance, i.e., it can withstand high or ultra high temperature over its life without the necessity of taking it apart and repacking it with lubricant.
The outer races for conventional bearings for furnace and sinter and pellet car wheels typically have diameters up to about 8 inches. The inner and outer races of such conventional bearings typically have thin cross-sections, i.e., on the order of xe2x85x9 to xc2xc inch. Bearing assemblies having such conventional bearings normally require a very tight or press fit between a bearing race and the shaft or housing in order to adequately support the bearing race. These special fits require high precision machining of either the shaft or housing to operate properly. The fits actually control the size and roundness of the races, effecting the running clearance of the assembly. These tight fits also require special tools and a great deal of care to prevent misalignment and to prevent surface damage to either the bearing or the shaft about which it is being mounted. In addition, after a period of time when the changing of the bearing is required, it is often difficult to remove the bearing, and special tools are often required therefor. The replacing of such a conventional bearing in the field, when required such as when a bearing has worn out, is thus a difficult process which may typically require as much as 6 hours. This work, which also requires special tools and/or special expertise, is thus considered more appropriate for skilled factory technicians than for workers in the field.
It is therefore also considered desirable to provide a bearing which in the field may be easily removed from and mounted to a wheel and axle without the need for special tools or special expertise.
Bearings having conventional tapered (conically shaped) rollers to bear against both radial and axial forces may tend to wear out quickly due to their inadequacy in handling axial loads, i.e., they are limited in the ability to handle high axial shocks.
It is accordingly an object of the present invention to provide a bearing which is low maintenance at high or ultra high temperature usage, i.e., it requires no repacking with grease during its useful life.
It is a further object of the present invention to provide a bearing which in the field may be easily removed from and mounted to a wheel and axle without the need for special tools or special expertise.
It is still another object of the present invention to provide such a bearing which has long life.
It is a further object of the present invention to provide an inexpensive, easy to manufacture, reliable bearing which has a minimum of parts.
In order to provide a low maintenance bearing which in the field may be easily removed from and mounted to a wheel and axle without the need for special tools or special expertise, in accordance with the present invention, the bearing is assembled as a cartridge with thick races and with a solid lubricant between the races.
In order to provide increased life to the bearing, it is provided with cylindrical rollers for bearing radial loads and with balls or spherical elements for handling axial loads.
In order to provide an inexpensive, easy to manufacture, reliable bearing which has a minimum of parts, in accordance with the present invention, the bearing is provided as two parts, i.e., an inner race and an outer race, with rolling elements therebetween, and a feeder slot is provided for loading the rolling elements between the inner and outer races.
The above and other objects, features, and advantages of the present invention will be apparent in the following detailed description of the preferred embodiments thereof when read in conjunction with the accompanying drawings wherein the same reference numerals denote the same or similar parts throughout the several views.